U8L4 Water Filtration

Question 1

What are the most common water purification methods?

Answer 1

• distillation
• filtering
• boiling
• adding chlorine

Question 2

How does distillation purify water?

Answer 2

By heating and cooling

Question 3

What is removed during distillation?

Answer 3

It removes a broad range of contaminants. As the water boils, most contaminants remain behind in the liquid. The process removes oxygen and minerals from water.

Question 4

What cannot be roomed during distillation?

Answer 4

Some contaminants can be carried into the water vapor

and can be found in the distilled water. Organics such as herbicides and pesticides cannot be removed.

Question 5

What is distilled water very acidic?

Answer 5

Distilled water has a lower pH and can also be very acidic.

Question 6

How costly is distillation?

Answer 6

It requires large amounts of energy and is very costly. Equipment must be carefully maintained to ensure purity.

Question 7

Where is distilled water usually used?

Answer 7

Distilled water is mainly used for industrial processes.

Question 8

What is the process of deionization remove?

Answer 8

This removes ions and dissolved inorganics through an ion exchange process.

Question 9

What doesn’t deionization remove?

Answer 9

It does not remove particles, organics, or microorganisms such as bacteria.

Question 10

How costly is deionization?

Answer 10

Over the long term, deionization has a high operating cost.

Question 11

What does carbon adsorption use to purify water?

Answer 11

This purifies water by using porous activated carbon (in granular or powder form).

Question 12

What processes does carbon adsorption use?

Answer 12

It involves physical and chemical processes.

Question 13

What does carbon adsorption remove?

Answer 13

It removes organic compounds, most chemicals and gases, and some
microorganisms.

Question 14

What doesn’t carbon adsorption remove?

Answer 14

It does not usually remove total dissolved solids, hardness, or heavy
metals such as lead. Some specialized carbon filters do remove things
such as lead or asbestos.

Question 15

How does carbon adsorption affect the taste and odor of water?

Answer 15

This helps improve the taste and odor of water.

Question 16

How costly is carbon adsorption?

Answer 16

It has a lower cost than other filtration types and is commercially
available to anyone. When the adsorption medium reaches its capacity, it has to be replaced. Carbon adsorption can be reversed; compounds can desorb after
capacity is reached.

Question 17

What does reverse osmosis use to purify water?

Answer 17

The process uses pressure to reverse the flow of water in a natural process of osmosis. Water passes from a more concentrated solution to a more dilute solution through a semi-permeable membrane filter.

Question 18

What is the pore size for a reverse osmosis filter?

Answer 18

0.0001 micron

Question 19

What does reverse osmosis remove?

Answer 19

This removes protozoa, bacteria, viruses, and common chemical contaminants such as sodium, copper, and lead.

Question 20

How costly is reverse osmosis?

Answer 20

It has a low cost and does not require much maintenance.

Question 21

How does reverse osmosis affect the pH?

Answer 21

This removes beneficial minerals and changes the pH of water, making it more acidic.

Question 22

How what does ultraviolet radiation use to purify water?

Answer 22

This process uses ultraviolet light to disinfect pre-filtered water or reduce the amount of bacteria found in the water.

Question 23

What does ultraviolet radiation remove?

Answer 23

It is highly effective at removing protozoa and bacteria.

Question 24

What doesn’t ultraviolet radiation filter out?

Answer 24

As there is no filter, heavy metals cannot be removed. It is inefficient at removing chemical contaminants

Question 25

When can ultraviolet radiation be used to purify water?

Answer 25

This can only be used with pre-filtered water or the particles can block UV light.

Question 26

What does ultrafiltration use to purify water?

Answer 26

This is a process by which water moves through a physical medium that absorbs liquids, gases, and other matter that adhere to the pores of the medium.

Question 27

What does ultrafiltration remove?

Answer 27

It effectively removes organics, such as protozoa, viruses, bacteria.

Question 28

What doesn’t ultrafiltration remove?

Answer 28

It does not remove most dissolved organics or common chemicals, such as lead, radium, or asbestos.

Question 29

How energy costly is ultrafiltration?

Answer 29

This process helps filter and produce a higher quality of water using the least amount of energy.

Question 30

What are jobs sewers?

Answer 30

Sewers collect the wastewater from homes, businesses, and many industries, and deliver it to
plants for treatment.

Question 31

What are the jobs of treatment plants?

Answer 31

Most treatment plants were

built to clean wastewater for discharge into streams or other receiving waters, or for reuse.

Question 32

How does the natural process of purification begin?

Answer 32

First, the sheer volume of clean water in the stream diluted wastes. Bacteria and other small organisms in the water consumed the sewage and other organic matter, turning it into new bacterial cells; carbon dioxide and other products. Today’s higher populations and greater volume of domestic and industrial wastewater require that communities give nature a helping hand.

Question 33

What is the basic function of wastewater treatment?

Answer 33

To speed up the natural processes by which water is purified.

Question 34

What happens in the primary stage of purification?

Answer 34

In the primary stage, solids are allowed to settle and removed from wastewater.

Question 35

What is the secondary start of purification?

Answer 35

The secondary stage uses biological processes to further purify wastewater.

Question 36

In the primary stage, there is a grit chamber. What does it do?

Answer 36

After sewage has been screened, it passes into a grit chamber, where cinders, sand, and small stones settle to the bottom. A grit chamber is particularly important in commu- nities with combined sewer systems where sand or gravel may wash into sewers along with storm water.

Question 37

What the job of the sedimentation tank?

Answer 37

After screening is completed and grit has been removed, sewage still contains organic and inorganic matter along with other suspended solids. These solids are minute particles that can be removed from sewage in a sedimentation tank.

Question 38

How does the sedimentation tank work?

Answer 38

When the speed of the flow through one of these tanks is reduced, the suspended solids will gradu- ally sink to the bottom, where they form a mass of solids called raw primary biosolids formerly sludge). Biosolids are usually removed from tanks by pumping, after which it may be further treated for use as a fertilizer, or disposed of in a land fill or incinerated.

Question 39

What is the problem with inky using primary treatment?

Answer 39

Over the years, primary treatment alone has been unable to meet many communities’ demands for higher water quality. To meet them, cities and industries normally treat to a secondary treatment level, and in some cases, also use advanced treatment to remove nutrients and other contaminants.

Question 40

How much organic matter in sewage does the secondary stage remove?

Answer 40

85 percent

Question 41

What is a trickling filter? What does it do?

Secondary treatment

Answer 41

A trickling filter is simply a bed of stones from three to six feet deep through which sewage passes. Bacteria gather and multi- ply on these stones until they can consume most of the organic matter. The cleaner water trickles out through pipes for further treatment. From a trickling filter, the partially treated sewage flows to another sedimentation tank to remove excess bacteria.

Question 42

Why is the activated sludge process used instead of the tricking filter?

Answer 42

The activated sludge process speeds up the work of the bacteria by bringing air and sludge heavily laden with bacteria into close contact with sewage.

Question 43

What happens in the aeration tank?

Answer 43

After the sewage leaves the settling tank in the primary stage, it is pumped into an aeration tank, where it is mixed with air and sludge loaded with bacteria and allowed to remain for several hours. During this time, the bacteria break down the organic matter into harmless by-products.

Question 44

During the end of the secondary treatment they use chlorine. What does chlorine do to the water?

Answer 44

Chlorine is fed into the water to kill pathogenic bacteria, and to reduce odor. Done properly, chlorination will kill more than 99 percent of the harmful bacteria in an effluent. Some municipalities now manufacture chlorine solution on site to avoid transporting and storing large amounts of chlorine, sometimes in a gaseous form. Many states now require the removal of excess chlorine before discharge to surface waters by a process called dechlorination. Alternatives to chlorine disinfection, such as ultraviolet light or ozone, are also being used in situations where chlorine in treated sewage effluents may be harmful to fish and other aquatic life.

Question 45

What is sludge?

Answer 45

Sludge is the mass of solids produced in the primary stage

Question 46

How is activated sludge better than trickling?

Answer 46

The activated sludge process speeds up the work of the bacteria by mixing new sewage with air and sludge filled with bacteria. After the sewage leaves the settling tank in the primary stage, it is pumped into an aeration tank, where it is mixed with air and sludge loaded with bacteria and allowed to remain for several hours. During this time, the bacteria break down the organic matter into harmless by-products. This sludge can also be reused again and again.

Question 47

Why is chlorine added?

Answer 47

Chlorine is added to disinfect, to kill pathogenic bacteria, and to reduce odor.

Question 48

What are some advanced wastewater treatment techniques and why are they needed?

Answer 48

Examples of advanced wastewater treatment techniques are filtration, carbon adsorption, distillation, and reverse osmosis. These techniques are being used to remove pollutants such as heavy metals, chemical compounds, and toxic substances.